Microwave enhanced deep fat fryer

ABSTRACT

A microwave radiation source is introduced into a fry basket within the fry tank of a deep fat fryer to reduce the cooking time of food products within the fry basket. Microwave energy is generated outside the fry tank and coupled into the fry basket by a microwave tuned transition, waveguide and antenna. Microwave chokes seal the basket top cover and microwave antenna to basket interface to confine the microwave energy to the fry basket. An electrical safety interlock prevents generation of microwave energy unless the fry basket is sealed.

This is a divisional of copending application Ser. No. 07/893,591, filedJun. 2, 1992, now abandoned which was a file wrapper continuation ofapplication Ser. No. 07/494,588, filed Mar. 16, 1990, now abandoned.

BACKGROUND OF THE INVENTION

This invention relates to microwave enhanced deep fat fryers for cookingfood products.

It is widely held that deep fat frying is the fastest traditional methodof cooking food by thermal energy alone. Deep fat frying imparts aspecial flavor to the food product as some of the cooking oil isabsorbed by the food product during the cooking process. Additionallyfood products cooked by deep fat frying exhibit an appealing crispytexture and brown appearance. Microwave cooking alone cannot match thetaste, texture or appearance of the food product cooked by deep fatfrying.

Customer feedback indicates that to be successful, high volume fast foodrestaurants must offer fast, hot, attractive and consistently cookedfood products. For high volume restaurants some deep fat fried foods,such as chicken nuggets, are normally fried ahead of time in a deep fatfryer and discarded if not sold within a few minutes. This is becausethe length of frying time is longer than the targeted order-placement toorder-filled time required for efficient fast food operation. Thismethod often detracts from the quality of the product when served sinceit may have been cooked many minutes earlier. Discarding cooked butunordered food products significantly increases waste. Microwaveenhanced deep fat frying to order within the target time produces ahotter, more consistent product, while maintaining its deep fat friedappearance, crispness and flavor.

Ideally, a microwave enhanced deep fat fryer should make efficient useof microwave energy by delivering it directly to the food product whileminimizing the use of microwave energy to heat the frying oil.Additionally, a microwave enhanced deep fat fryer should require nospecial training to use, have the same form and require no more floorspace than current non-enhanced deep fat fryers.

SUMMARY OF THE INVENTION

A general feature of the invention is the provision of a microwaveenhanced deep fat fryer with a fry tank containing heated cooking oil,an oil porous cooking vessel such as a wire basket, for immersing foodproducts in the oil, and means for introducing and confining microwaveenergy within the same cooking vessel. One preferred embodiment heatsthe cooking oil with a typical natural gas fired fire tube.

Another general feature of the invention comprises introduction of themicrowave radiating source from within a removable cooking vessel. Inthe preferred embodiment this is achieved by forming a conical recess,in the bottom of the basket, into which a microwave antenna isintroduced. A coaxial waveguide is coupled and tuned to the antenna inthe cooking vessel to transfer microwave energy from a microwave energysource to the antenna. A magnetron microwave source generates microwaveenergy which is coupled to the coaxial waveguide by a rectangulartransition waveguide positioned between the magnetron and the coaxialwaveguide.

A further aspect of the invention includes microwave chokes associatedwith the cooking vessel to prevent microwave energy leakage out of thecooking vessel. One preferred embodiment combines a microwave tightsteel mesh cooking vessel, a microwave choke embedded in the cookingvessel cover, and another microwave choke around the cooking vessel tocoaxial waveguide interface.

Yet another aspect of the invention includes an electrical safetyinterlock to prevent undesirable activation of the microwave energy. Onepreferred embodiment uses a safety interlock responsive to the positionof the cooking vessel cover to control activation of the magnetron.

DESCRIPTION OF THE PREFERRED EMBODIMENT

A brief description of the drawings is as follows:

FIG. 1 is a side view of a microwave enhanced deep fat fryer showing therelationship of the microwave generators and waveguides, fired heatingapparatus and one of two fry basket microwave reactors.

FIG. 2 is a cross-sectional plan view of the microwave enhanced deep fatfryer of FIG. 1, showing the microwave generating apparatus includingmagnetrons, magnetron cooling fans, transition couplings and coaxialmicrowave waveguides for the twin basket reactors.

FIGS. 3-6 are side, plan, front and back views of the fry basketmicrowave reactor of FIG. 1, respectively, showing steel frameconstruction, microwave impenetrable steel mesh, microwave antennasaddle and associated microwave saddle seal.

FIG. 7 is a plan view of the side-by-side fry basket reactors positionedwithin the fry tank of FIG. 1, each covered by its own hinged microwavetrapping fry basket cover.

FIG. 8 is a plan view of the microwave choke attached to the undersideof each fry basket cover of FIG. 7.

FIG. 9 is a side view of the microwave choke of FIG. 8.

FIG. 10 is a rear view of the fryer of FIG. 1 showing the electricsafety interlock mechanism.

FIG. 11 is a detail view of the rear portion of the fryer of FIG. 1showing the electric safety interlock switches and associated camresponsive to the position of the cover of FIG. 7.

FIG. 12 is a detail longitudinal cross-section side view of themicrowave producing magnetron taken along lines 12--12 of FIG. 2,showing the waveguide transition coupling, the longitudinal coaxialwaveguide terminated in a microwave radiating antenna in an antennahood, and a portion of the fry basket reactor interface choke.

FIG. 13 is a cross-sectional side view of the microwave antenna to frybasket reactor interface taken along lines 13--13 of FIG. 1, showing theoperational microwave choke and the relationship of the antenna hood tothe fry basket saddle.

FIG. 14 is a cross-sectional view of the slotted 1/4 wavelengthmicrowave choke element of FIG. 13.

STRUCTURE

As shown in FIGS. 1 and 2, a microwave enhanced deep fat fryer 10employing conventional heating combined with advanced microwave cookingtechnology designed primarily for commercial restaurant operation isdesigned to be a free standing dual basket deep fat fryer configuration.A preferred embodiment incorporates a microwave cooking system as amodification to a stand alone gas fired dual basket deep fat fryer suchas a Decathlon 35, commercially available from Dean Alco Corp., LosAngles, Calif., incorporated herein by reference.

Cabinet 12 has a cavity or fry tank 16 designed to accept two side byside fry basket reactors (one shown) 17 containing food product to besimultaneously fried and microwaved. The fry tank 16 holds apredetermined level of frying oil into which the fry basket reactors 17holding food product are immersed. A series of four conventional gasfired fire tubes 20 heat the fat to a temperature sufficient to causedeep fat frying of the food product immersed in the heated cooking oil.

A pair of coaxial microwave waveguides 22 (FIG. 2) are positioned in thefry tank below the center of each fry basket reactor 17 to introducemicrowave energy directly into the basket by means of an antennaprotruding through the bottom of each basket. Each elongated microwavecoaxial waveguide 22 extends up from microwave transition waveguide 24through aperture 25 in the bottom of the fry tank cavity 16 and isterminated in an antenna that fits into fry basket saddle 132. Microwavegenerating magnetrons 26 develop the required microwave energy which istransferred through coaxial microwave waveguides 22 to cook the foodproduct in the baskets 17. Cooling fans 28 provide cooling to each ofthe two magnetrons 26. Gas fired fire tubes 20, fired by gas burners 21,extend the length of the fry chamber 16. The fire tubes 20 are incontact with the frying oil in fry tank 16 and thereby heats the oil toits frying temperature. Fire tube exhaust gasses 23 are ported out ofthe fryer through chimney 27. The coaxial waveguides 22 are small enoughto pass through the space between the standard gas fired fire tubes 20without significantly altering the form or positioning of the firetubes. Additionally, the microwave component packaging is such that allfryer options are available including the bulky roll away filter 30standard on most deep fat fryers.

As shown in FIGS. 3-6, fry basket reactor 17 has two long sides 40, twoends 42 and a bottom 44, made of stainless steel wire mesh 46 formedaround a rigid stainless steel frame 48. The size of the openings 47 inthe stainless steel mesh 46 is closely controlled to prevent microwaveleakage out of the basket, while allowing free circulation of hot oilthrough the basket. A handle 50 angularly extends out from one end 42above basket opening 52 to allow easy manual immersion of the basketinto and out of hot fry tank 16. Basket opening 52 has a rectangularperipheral lip 54 surrounding and extending out from the edge of theopening 56.

A central aperture 124 is disposed in the bottom 44 of the basket 17 toaccommodate the microwave antenna assembly 80 (FIG. 1). Cone shapedTeflon basket saddle 132 (TEFLON is a registered trademark forpolytetrafluroethylene materials) is shaped to accept antenna assembly80 and prevents food product from falling through aperture 124. Basketsaddle 132 is made of a high temperature tolerant, low microwave lossmaterial. Additionally, microwave basket seal 126 is an annularcomponent surrounding the aperture 124 which when placed over the chokecomponents of antenna assembly 80 prevents leakage of microwave energythrough aperture 124, as discussed below in conjunction with FIGS. 12and 13.

FIG. 7 shows the microwave tight door assembly 60 positioned over eachof the side by side fry basket reactors 17 positioned in fry tank 16.The two door assemblies 60 are symmetrically identical, so only the leftassembly in FIG. 7 will be described. Stainless steel door 62 is hingedto the top rail 64 of the fryer cabinet 12 by a hinge rod 66 extendinglongitudinally from hinge base 68 to and beyond hinge bearing 70. Doorhinge portion 72 is fixed to hinge rod 66 between hinge base 68 andhinge bearing 70 so that rod 66 rotates when door 62 is opened orclosed. Door 62 pivots about the longitudinal axis of rod 66 to coverbasket 17 within fry tank 16, or remain open (not shown) while basket 17is being placed in or removed from fry tank 16. Hinge rod 66 extendsbeyond hinge bearing 70 to operate an electric microwave safetyinterlock (FIG. 11) responsive to the position of door 62 as translatedby the rotation of rod 66.

A microwave choke assembly 74 is attached to the underside 76 of door 62to contact the entire peripheral edge 56 of the basket opening 52,thereby creating a microwave tight seal between the door 62 and thebasket 52. This seal, combined with microwave tight basket mesh 46 andmicrowave antenna seal 126 (FIG. 13) discussed below, make the interiorof basket 17 a microwave tight reactor vessel for the microwave cookingof food products.

FIGS. 8 and 9 show the construction of the microwave choke 74, attachedto the underside 76 of door 62, used for sealing the top of the frybasket reactor 17 in fry tank 16 when cover 62 is closed over thebasket.

Microwave choke 74 is fashioned as a rectangular frame protruding fromthe substantially planar surface 76 of stainless steel door 62. Interiorperipheral wall 78 is disposed normal to surface 62 and is welded alongits entire interface 81 with surface 76 to define the rectangularinternal microwave tight wall of the choke. The choke face 83 extendsfrom the edge of interior peripheral wall 78 opposite interface 81,toward the outer edges of cover 62, with the face 83 being substantiallyparallel to cover surface 76. Choke contact surface 85 forms the outerperipheral surface of choke 74. Contact surface 85 extends from outerperipheral edge 87 of face 83 toward surface 62 at a small angle A (FIG.9) away from interior peripheral wall 78. This angle causes the contactsurface 85 to resiliently urge against the peripheral edge 56 of basketopening 52 (FIG. 7) when door 62 is closed over basket 17 in fry tank16. Additionally, contact surface 85 has a series of notches 89 cut toprevent circulation of microwave currents on the surface of the choke.

FIGS. 10 and 11 show a cover controlled safety interlock mechanism whichonly energizes the microwave system when a basket 17 is properly inplace in fry tank 16, the cover choke 74 is in place, and the cover 62is closed over the basket. Only the right side mechanism (left side ofFIG. 10 and 11) is shown and discussed since the left side mechanism issymmetrically identical. Hinge rod 66 extends through hinge bearing 70,through rod supports 200 and terminates in actuator arm 202 which isdisposed at a right angle to rod 66. Rod 66 passes through the proximalend 204 of actuator arm 202, which is mechanically fixed to rod 66 bybolts 206, so that the distal end 208 of actuator arm 202 pivots aboutthe longitudinal axis of rod 66 to sweep through arc 210 when door 62 isopened or closed. Safety interlock cam 212 is connected to the distalend 208 of actuator arm 202, and communicates with three safetyinterlock switches 214, 216, 218 by means of cam edges 215, 217, 219respectively, as it is swept through arc 210.

FIG. 11 shows switches 214, 216 and 218 in the activated position.Switch 218 activates the microwave support circuitry, while switches 214and 216 activate the supplying energy to its associated antenna.Switches 214 and 216 are wired is series, thus creating a redundancypreventing inadvertent activation in the case where one of the switchesfails by shorting closed. As the cover sweeps from fully open (notshown) to fully closed (as illustrated), cam edge 219 activates switch218, first, thereby activating the electronics prior to magnetronactivation by switches 214 and 216. Switch 218 remains active throughoutthe remainder of the sweep allowed for door 62 as it goes toward, andpossibly past its fully closed position as shown.

Magnetron activator switches 214 and 216 operate over only a very narrowrange of the arc swept by cam 212, as is apparent by the relativelysmall activation area of cam surfaces 215 and 217. This narrow rangecorresponds to the door 62 being positioned as shown in FIG. 11, aposition substantially parallel to the top of the fry basket reactor 17in fry tank 16. This positioning can only occur when the cover choke 74(FIG. 7) is fully engaged with the peripheral edge 56 of the fry basket17. An angular variation as small as 5° from this position will shutdown the magnetron. Further, if either the cover choke assembly 74 ismissing or the fry basket reactor 17 is not in fry tank 16, the coverwill go beyond its fully activated position, causing activator arm 202to contact activator arm stop 220, and magnetron switches 214 and 216 tobe deactivated by cam surface portions 222 and 224 respectively.

FIG. 12 shows a longitudinal cross-section view of the microwave energytransmission system of this invention including microwave transitionwaveguide 24, coaxial waveguide 22 and microwave antenna assembly 80.Magnetron 26 develops microwave energy at magnetron output antenna 82which is disposed part way into the rectangular microwave transitioncavity 84 formed by the metal sides transition of box 86 which definestransition waveguide 24. Coaxial waveguide 22 input probe 88 is alsodisposed part way into transition cavity 84. The dimensions of thetransition cavity 84, the placement of the magnetron output antenna 82,and the placement and diameter of coaxial waveguide input probe 88 arechosen to maximize the microwave energy transfer from magnetron antenna82 to coaxial waveguide 24.

Coaxial waveguide 22 includes a cylindrical outer conductor constructedof 1" O.D.×0.065" wall 304 stainless steel tubing. Coaxial waveguidecenter conductor 92 is constructed of 0.38" diameter aluminum rod, andis held coaxially inside outer conductor 90 by Teflon retaining rings94. A partially spherical probe 88 is threadably attached to the end ofthe center conductor 92 disposed in the transition cavity 84. A 1/2wavelength long antenna matching transformer rod 96, having a diametervariable with respect to the diameter of inner conductor 92, isthreadably attached between the antenna assembly 80 end of the centerconductor 92 and antenna 98 to electronically match the coaxialwaveguide 24 to the antenna 98. Antenna 98, disposed outside the end ofouter conductor 90 inside Teflon antenna hood 100, is a 0.38" diameteraluminum rod threadably attached to the 1/2 wavelength transformer 96.The diameter of the 1/2 wavelength transformer 96 depends on the lengthof antenna 98, and is chosen to maximize the microwave energytransferred from the coaxial waveguide 22 to the antenna 98.

The coaxial waveguide 22 is mechanically attached to the transitionwaveguide 24 by coupling assembly 102. Coupling assembly 102 includes anannular collar 104 circumferentially welded 106 to the outer conductor90. Annular collar 104 mates with cylindrical coupler 108 which iscircumferentially welded 110 to transition box 86. A coaxialcounter-bore 112 in the coupler 108 accepts one end of the coaxialwaveguide outer conductor 90. An annular groove 114 cut in the outersurface of coupler 108 accepts set screws 116 threadably disposedthrough collar 104 to allow tight mechanical and electrical coupling ofthe collar 104 to the coupler 108, thereby preventing microwave energyleakage through coupling assembly 102.

FIG. 13 shows a cross-sectional view of antenna assembly 80 coupled tofry basket reactor 17 to form a microwave tight reactor vessel 120.Microwave choke assembly 122, incorporated into the antenna assembly 80interface, to basket 17 prevents microwave energy from escaping from thereactor vessel 120 through aperture 124 in basket 17 which is requiredto accept antenna assembly 80. Construction of a similar microwave chokewas described Harhen in U.S. Pat. No. 3,789,178, incorporated herein byreference.

Basket seal 126 is a metallic cylindrical sleeve attached to the edge125 of aperture 124, extending longitudinally outside the basket tosurround the remainder of the choke assembly attached to coaxialwaveguide 22. One end of basket seal 126 is circumferentially welded at128 and 129 to aperture edge 125 in basket 17 to form a microwave-tightjoint. The same end of basket seal 126 is internally threaded 130 toaccept threaded Teflon basket saddle 132. Basket saddle 132 is shaped toaccept antenna hood 100 without interference. Basket seal 126 isdimensioned to sit on choke base 134, attached to coaxial waveguideouter conductor 90, to support basket 17 when basket saddle 132 isplaced on top of antenna assembly 80.

Choke base 134 is a metallic annular disk, radially disposed aroundcoaxial waveguide outer conductor 90 and attached by means of a centralannular flange 136. Annular flange 136 is circumferentially welded toouter conductor 90 to form a strong mechanical and microwave tightjoint. Basket seal 126 annularly contacts choke base 134 at annularinterface 138.

Antenna choke element 140 is a metallic cup having circular surface 142with perpendicular cylindrical 144. Outer coaxial conductor 90 isdisposed through a central aperture 146 in antenna choke elementcircular surface 142 so that cylindrical surface 144 is coaxial withouter conductor 90. Antenna choke central aperture 146 iscircumferentially welded at 148 to outer conductor 90 between choke base134 and the antenna end 149 of outer conductor 90 so that cylindricalsurface 144 extends longitudinally from circular surface 142 towardchoke base 134, leaving a small gap 150 between the annular edge 152 ofcylindrical surface 144 and the surface of choke base 134. The annularspace 156 around the outer conductor 90, substantially enclosed by theantenna choke element 140 and the choke base 134, is filled with aTeflon ring 157 to prevent debris from entering and accumulating in thespace 156 through gap 150.

A cylindrical internally threaded flange 158 is connected to chokecircular surface 142 directly opposite cylindrical surface 144 tothreadably attach Teflon antenna hood 100 to the coaxial waveguideassembly 22. A metallic ring 160 having a silicone o-ring 162 disposedin an annular grove in its external surface is disposed between outerconductor 90 and antenna hood 100 to effectively seal the antennacompartment 164 from the hot cooking oil in which it is immersed.

FIG. 14 shows a longitudinal cross-sectional view of antenna chokeelement 140. Multiple longitudinal slots are distributed around thecircumference of cylindrical surface 144 to effectively eliminate anymicrowave currents that may circulate on surface 144. The dimension A ofcylindrical surface 144 is 1/4 wavelength of the microwave energy. Thecombination of the 1/4 wavelength surface 144, its position adjacent tobasket seal 126 (FIG. 13) and annular gap 150 prevent microwave energyfrom leaking out of the basket seal/choke base interface 138. The chokefunctions by diverting energy that reaches gap 150 back along 1/4wavelength surface 144 to system ground at choke element circularsurface 142.

Referring again to FIG. 13, four Teflon plates 166 are disposed adjacentto the bottom 44 and short sides 42 of the fry basket reactor 17. Aseries of holes 168 are disposed through each Teflon plate 166 to allowoil to circulate through the plates. The Teflon plates allow somemicrowave energy to travel through the plates and bypass food productsin close proximity to antenna assembly 80, and thereby provide a moreuniform microwave energy distribution among all food products in thebasket 17. The result is a uniformly heated food product independent ofits location within the basket 17.

OPERATION

Cooking tests of the microwave enhanced deep fat fryer of this inventionwere performed on 2 lbs. of frozen (-12° C.) breaded chicken nuggetsweighing about 0.7 ounces (19 grams) each. The fry basket reactor wasremoved from the fryer and the nuggets were arranged uniformly in thebottom of the fry basket reactor. The level of cooking oil in the frytank was sufficient to cover all the food product as arranged in the frybasket reactor when the reactor was properly positioned in the fry tank.The gas fired fire tubes were ignited and allowed to raise and maintainthe temperature of the cooking oil in the fry tank to 177° C. Then, thefry basket reactor was lowered into the fry tank. Promptly, the frybasket reactor cover was closed which activated the microwave energyapplied to the reactor. 700 Watts of microwave energy was introducedinto the fry basket reactor for 2 minutes and 45 seconds, after whichthe cover was opened and the reactor promptly removed from the fry tank.

The temperature of the chicken nuggets, fried as described above, wasraised from a frozen starting internal temperature of -12° C. to anending internal temperature of 76 -91° C. in a little over 2 minutes and45 seconds. The product quality was excellent, exhibiting uniformcooking; crisp and brown outside, juicy and tender inside. A comparabletime required to obtain this temperature rise by frying alone is about 4minutes. Thus, microwave enhanced deep fat frying reduced cooking timein this case by 31%.

Similar tests performed on other food products showed cooking timesavings of between 15% and 50% oven frying alone, with excellent qualityresults.

ADVANTAGES

The microwave enhanced deep fat fryer technology described above hascompelling advantages in the preparation of deep fat fried fast foods incommercial establishments, particularly in accelerating the cooking offrozen food products to fully cooked with upwards of 50% decrease incooking time over conventional deep fat fryers. This is highly desirablesince it allows deep fat fried food products to be cooked to orderrather than being prepared in advance and reheated to fill an order.Such cooking to order substantially contributes to high product qualityand consistency.

A highly desirable feature of the invention is the ability to preparedeep fat fried foods in less time while retaining the flavor, crispnessand color of a deep fat fried food product. The-invention combines thespeed of microwave cooking with the product qualities of deep fat friedfoods in a manner that produces consistently excellent results.

Another highly desirable feature of the invention is the ability toapply the microwaves directly to the food product in a smallmicrowave-tight enclosure, thereby enhancing the control of microwavecooking energy applied to the food product. This results in consistent,predictable and well controlled cooking of the food product, whileminimizing the amount of microwave energy used. Energy savings areenhanced since only a minimal amount of microwave energy is diverted toheating the cooking oil in the fry tank reservoir.

The use of advanced microwave energy chokes and electrical safetyinterlocks provide the advantages of mechanical simplicity while makingthe invention safe and easy to use. Small size of the microwave enhancedfryer makes it ideal for fast food establishments where floor space isoften at a premium. One preferred embodiment described herein is amodification of a standard commercial deep fat fryer that retains all ofthe original features including the standard roll-away oil filter andthe original footprint of the unmodified commercial unit.

The foregoing description has been directed to specific embodiments forthe purposes of illustration. Many variations and modifications designedfor the same applications or other applications are possible withoutdeparting from the principles of the invention. Other embodiments arewithin the spirit and scope of the invention as claimed below.

What is claimed is:
 1. A cooking vessel for use with a microwave enhanced deep fat fryer wherein microwaves are introduced into said cooking vessel by microwave introducing means within said cooking vessel, said cooking vessel comprising:an open topped basket having elongated side, end, and bottom oil porous surfaces, said surfaces being substantially impenetrable to microwave energy; a handle extending from one said end surface; and an indentation centrally located in said bottom surface for accepting the microwave introducing means.
 2. The cooking vessel of claim 1, wherein said indentation includesan aperture in said bottom of said basket; and an aperture cover attached to and extending into said basket to enclose said aperture, said aperture cover being made of a high temperature tolerant, low microwave loss material; wherein said aperture and said aperture cover are sized and shaped to accept the microwave introducing means.
 3. The cooking vessel of claim 2 wherein said aperture cover is conically shaped.
 4. The cooking vessel of claim 2 wherein said aperture cover is made from polytetrafluroethylene.
 5. The cooking vessel of claim 2 wherein said aperture cover is threadably engaged with said cooking vessel.
 6. The cooking vessel of claim 2 wherein said elongated side, end and bottom surfaces comprises metallic mesh sized to substantially prevent the escape of microwave energy.
 7. A microwave fry basket comprising:a bottom surface and side surfaces made of porous metallic material designed to substantially confine microwave energy within said basket; an aperture in one of said surfaces; and an indentation made of microwave transparent material, said indentation positioned over said aperture and extending into said basket.
 8. The basket of claim 7 wherein said indentation is conical with a base generally at the bottom surface of the basket.
 9. The basket of claim 7 further comprising a metal sleeve coupled to the porous metallic bottom surface at the aperture, said sleeve forming a microwave seal.
 10. A cooking vessel for use with a microwave enhanced deep fat fryer comprising:a bottom surface and side surfaces defining an opening for introducing food articles into said vessel, at least one of said surfaces being porous and having passages which allow entry of cooking oil into said vessel, said passages sized to substantially confine microwave energy within said vessel; an aperture in one of said surfaces for introducing a microwave energy source into said vessel; and an aperture cover positioned over said aperture and extending into said vessel so as to allow introduction of the microwave energy source into said vessel, said aperture cover being made from temperature resistant, low microwave loss material.
 11. The cooking vessel of claim 10 wherein said porous surface is made from mesh.
 12. The cooking vessel of claim 11 wherein said mesh is stainless steel.
 13. The cooking vessel of claim 10 wherein said aperture cover is made from polytetrafluroethylene.
 14. The cooking vessel of claim 10, further comprising a sleeve surrounding said aperture, said sleeve forming a microwave seal.
 15. The cooking vessel of claim 10, further comprising a peripheral lip surrounding said opening, said peripheral lip forming a microwave seal.
 16. The cooking vessel of claim 10, further comprising a handle extending from one of said side surfaces.
 17. A metallic mesh fry basket for a microwave-enhanced deep fat fryer having a bottom and an aperture in the bottom of the basket covered by a temperature resistant, low microwave-loss material through which microwave energy may be introduced into the basket, the mesh being sized to contain said microwave energy within said basket. 